The present invention relates to lithographic printing plate supports and presensitized plates.
A conventional presensitized plate widely used includes a hydrophilic aluminum support for lithographic printing plates (hereafter referred to as “lithographic printing plate support”), and an lipophilic, photosensitive layer provided on the support. The presensitized plate as such is subjected to mask exposure through a lith film, then to developing treatment for dissolving non-image areas to remove them, so as to obtain a desired lithographic printing plate.
In recent years, computer-to-plate (CTP) technology is also employed to manufacture a lithographic printing plate with no lith films by performing a scan with light of high directivity, such as a laser beam, in accordance with the digitized image information.
The lithographic printing plate support as above is obtained by subjecting an aluminum plate to such treatments as graining treatment and anodizing treatment.
During the preparation of the support, anodizing treatment may be followed by sealing treatment with water vapor for the improvement in various properties. As an example, JP 04-176690 A discloses sealing treatment carried out “in a chamber saturated with vapor at 100° C. under 1 atmosphere” (page 9).
JP 59-114100 A discloses the treatment with water vapor to be conducted after anodizing treatment under such conditions that the temperature is 120° C., the water vapor pressure is 700 Torr, and the treatment time is 10 seconds (Table 2 on page 9).